Vitamin D3, K2, and Testosterone: What Evidence Shows

By Noophoric Editorial Team Updated August 30, 2026

Vitamin D3 and vitamin K2 support several systems that matter to men, including bone health, calcium metabolism, immune function, and normal endocrine physiology. Low vitamin D status is often associated with lower testosterone in observational research, and some trials report a modest testosterone benefit from vitamin D supplementation. Other trials do not, so the most useful goal is adequate vitamin D status rather than treating D3 or K2 like hormone replacement.

The two vitamins are frequently paired because vitamin D helps the body absorb calcium while vitamin K activates proteins involved in bone mineralization and calcium regulation. That relationship can be valuable regardless of whether a man experiences a measurable testosterone change.

Vitamin D acts more like a hormone than a typical vitamin

After vitamin D is produced in the skin or absorbed from food and supplements, the body converts it into active metabolites that bind to vitamin D receptors throughout many tissues. These receptors are involved in gene expression, immune signaling, bone metabolism, and other functions.

Men can fall short because of limited sun exposure, darker skin pigmentation, older age, malabsorption, obesity, restrictive diets, or certain medications. A blood test called 25-hydroxyvitamin D is commonly used to assess status.

What studies show about vitamin D and testosterone

Observational studies frequently find that men with lower vitamin D levels also have lower testosterone. That does not prove one causes the other because body weight, physical activity, chronic illness, sleep, and diet can influence both.

Randomized trials provide mixed results. A 2024 meta-analysis found a small increase in total testosterone with vitamin D supplementation but no clear effect on free testosterone or several other hormone measures. A larger 2026 meta-analysis found no statistically clear testosterone benefit overall and rated the evidence as low certainty because the studies differed in participants, doses, duration, and baseline vitamin D status.

Together, the research supports correcting low vitamin D for established health reasons. It does not support assuming that more vitamin D always produces more testosterone.

Where vitamin K2 fits

Vitamin K2 activates proteins involved in normal coagulation and bone metabolism. Preclinical research with MK-4 has shown increased testosterone production in rats and testicular cells, but direct human testosterone trials are lacking.

That makes K2 a complementary foundational nutrient, not the ingredient on which a testosterone claim should rest. Read our focused review of vitamin K2 and testosterone for the difference between animal evidence and human outcomes.

D3 and K2 work within calcium and bone metabolism

Vitamin D increases intestinal calcium absorption. Vitamin K is required to activate osteocalcin and other proteins. Protein intake, magnesium, weight-bearing exercise, hormones, and total calcium intake also influence bone strength.

This matters for men because low testosterone can contribute to loss of bone density. Supporting bone health throughout adulthood is useful even when testosterone is normal. A supplement should complement resistance training and a balanced diet rather than replace them.

How D3 and K2 fit in men’s formulas

Vitamin D3 and K2 can appear in both foundational nutrition products and broader testosterone-support formulas. The best choice depends on the rest of the label and the intended goal.

Noophoric D3 + K2 Complex provides 5,000 IU of vitamin D3, 100 mcg of vitamin K2, 210 mg of calcium, and BioPerine in each serving to support bone health, immune function, and normal calcium metabolism.*

Noophoric Men’s+ includes 3,000 IU of vitamin D3 and 100 mcg of vitamin K2 alongside zinc, boron, ashwagandha, tongkat ali, fenugreek, Coleus forskohlii, and other ingredients selected to support healthy testosterone levels, energy, drive, and resilience.*

How much vitamin D is appropriate?

The recommended dietary allowance for most adults is 600 IU per day and rises to 800 IU after age 70. These recommendations are designed for general nutritional adequacy, while clinicians sometimes recommend higher amounts based on blood levels, absorption, body size, or medical needs.

The adult tolerable upper intake level is 4,000 IU per day for routine unsupervised intake. A product containing 5,000 IU may be appropriate for some adults, but it is especially important to consider baseline status, total intake from other products, and periodic testing when used long term.

Can you get D3 and K2 from food?

Fatty fish, egg yolks, liver, fortified dairy alternatives, fortified milk, and some mushrooms provide vitamin D, though it can be difficult to meet needs through food alone. Vitamin K1 is abundant in leafy greens. Vitamin K2 occurs in natto, certain cheeses, egg yolks, and animal foods in varying amounts.

Sunlight can support vitamin D production, but season, latitude, skin pigmentation, clothing, sunscreen, age, and skin-cancer precautions make a universal sun prescription inappropriate.

Safety and interactions

Excess vitamin D can cause hypercalcemia, leading to nausea, weakness, confusion, excessive thirst and urination, kidney stones, or kidney injury. The risk usually comes from high-dose supplements rather than sun exposure.

Vitamin D and calcium may interact with certain thiazide diuretics and other medications. Vitamin K can interfere with warfarin and related vitamin K antagonist anticoagulants. People taking these drugs should not change vitamin K intake without guidance.

Check every label if you use a multivitamin, calcium product, D3 product, and men’s formula together. Duplication can quietly push total intake higher than intended.

How to build a complete testosterone-supportive routine

Vitamin status is only one part of male wellness. Aim for consistent sleep, progressive resistance training, adequate energy and protein, a healthy waist circumference, moderate alcohol intake, and treatment of medical problems such as sleep apnea.

If you have persistent symptoms, read our guide to low testosterone symptoms, causes, and testing. A diagnosis requires more than fatigue or one afternoon blood test.

Frequently asked questions

Can vitamin D3 raise testosterone?

Some trials and a 2024 meta-analysis suggest a small increase in total testosterone, while other analyses do not find a clear overall effect. Men who are deficient may have more reason to benefit than men who already have adequate status.

Does vitamin K2 raise testosterone?

MK-4 increased testosterone production in animal and cell studies, but controlled human evidence is not yet available. K2 remains useful for its established vitamin K and bone-related roles.

Why take D3 and K2 together?

D3 supports calcium absorption and K2 activates vitamin K dependent proteins involved in bone metabolism. They are complementary, although neither vitamin eliminates the need to consider total calcium, magnesium, protein, exercise, and medication.

Should I test vitamin D before supplementing?

Testing is especially useful if you plan to use a higher dose long term, have risk factors for deficiency, have kidney or parathyroid disease, or already take several products containing vitamin D.

Can D3 and K2 replace testosterone therapy?

No. They are nutrients. Clinically confirmed hypogonadism requires evaluation of the cause and individualized treatment discussions.

Bottom line

Vitamin D3 and K2 support bone, immune, and calcium-related functions that matter throughout a man’s life. Vitamin D’s relationship with testosterone is plausible and supported by some human data, but supplementation results are mixed. K2’s testosterone evidence remains preclinical. Use these nutrients to build adequacy within a complete routine, not to chase unlimited hormone increases.

Sources

Evidence reviewed August 2026. This article is educational and is not a substitute for individualized medical diagnosis or treatment. *These statements have not been evaluated by the Food and Drug Administration. Noophoric products are not intended to diagnose, treat, cure, or prevent any disease.